Fig.3(a) shows the zero-field cooled(ZFC) and field-cooled(FC) magnetization curves for SIO-as prep and SIO-anneal samples at an applied magnetic field of 1T. Both the samples exhibit magnetic transition below around \(\sim \) 238 K as seen from the inflexion point in the derivative of the ZFC magnetization curve, inset of Fig.3(a). The inverse susceptibility shown in Fig.3(c) do not obey Curie-Weiss behaviour in the entire paramagnetic region of both the samples, but in a limited temperature region. The transition temperature (T\(_{N}\) ) obtained from the fitting are 233.7 K and 233.8 K, respectively for SIO-as prep and SIO-anneal samples. The estimated effective paramagnetic moment \(\mu _{eff}\)  value for SIO-as prep is \(\sim \) 0.58\(\mu _B\)  which is close to reported values[1]} while \(\mu _{eff}\)  for SIO-anneal is \(\sim \) 0.60\(\mu _B\) ,higher than SIO-as prep. The transition temperature marks the transition from paramagnetic to canted antiferromagnetic structure. The rise in the dc magnetization below T\(_{N}\)  suggests weak ferromagnetic behaviour arising due to the canted antiferromagnetic structure. The magnetic structure of Sr\(_{2}\) IrO\(_{4}\)  compound is shown in Fig.1(d). The J\(_{eff}\) =1/2 pseudospins are rotated in the ab-plane by about 13\(^\circ \)  and are locked to in-plane IrO\(_6\)  octahedral rotation due to strong spin orbit coupling.[2]} This canting of spins results in a net magnetic moment along b-direction in each Ir-O layer which are arranged in (\(\uparrow \downarrow \downarrow \uparrow \) )manner along c-direction as shown in Fig.1(d).[2]}, [4]} The intralayer magnetic interaction which is dominated by Heisenberg exchange coupling (\(\sim \) 60meV) is stronger compared to interlayer interaction.[5]} Both these interactions (intra and interlayer) are proposed to be necessary to stabilize the observed canted AFM magnetic structure.[6]} The canting of moments in the ab-plane arises due to DM-interaction which is responsible for weak ferromagnetic behaviour of the compound.
